London, April 23 (Reuters): When Lorna Wadsworth was invited to paint at a conference of Tony Blair's Labour Party, she lurked in halls and outside rooms until she won a rare sitting with the Prime Minister.

'I had been stalking him all conference, because obviously he was the prize beast. I had been kind of lying in wait for him, following him around,' the 25-year-old portrait painter said today.

'When I finally got my sitting with him he said: 'Oh, it's you!' Because he had been worrying who this crazy blonde girl was. So I guess he was relieved to learn I was not a maniac.' The result, a pensive, brooding Blair, goes on display on April 28, alongside her renditions of other key government and party figures, at the Royal Society of Portrait Painters' annual exhibition in London.

Despite having arguably one of the most distinctive faces in British political history ' beloved of caricaturists, mocked by opponents ' Blair has rarely sat for formal portraits.

Wadsworth got him to sit in a hotel room on the sidelines of the party's conference in 2003, at a time when Labour was riven over Blair's decision to join the US in war in Iraq and the Prime Minister's own future was being cast into doubt.

Blair is joined in the series by top party luminaries, including former cabinet ministers Clare Short and Robin Cook who resigned angrily over the war. Short scowls severely, but Cook, a former foreign secretary, smiles cheerfully.

Wadsworth said she was fascinated by Blair's face.

'It's interesting: it's very angular. He's got very pronounced cheek bones. He has got incredibly blue eyes in real life. Almost disconcertingly blue.' The trick is capturing the true personality of a politician in an era when leaders obsessively manage their images.

'I think in this age, more than any other, it matters what a politician looks like. Nowadays they have to be TV friendly, the right tie with the right suit,' she said.

'Part of being a politician in today's day and age is controlling what appears on your face.'